Optical communication interface module connected to electrical communication interface module of I2C communication protocol

ABSTRACT

An optical communication interface module connected to a direct-current (DC) power terminal, an input/output (I/O) terminal and a ground terminal, to perform optical communication. The module includes a PNP transistor for transmission, a pull-up device, a photo generator device, a photoelectric converter, and first and second NPN transistors for reception. The PNP transmission transistor has its base connected to the I/O terminal and its collector connected to the ground terminal. The first transistor for reception with its collector connected to the anode of the photo generator device and its emitter connected to the ground terminal, has its base driven by output signals of the photoelectric converter. The second transistor for reception with its collector connected to the I/O terminal and its emitter connected to the ground terminal, has its base driven by an output signal of the photoelectric converter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical communication interface module connected to an electrical communication interface module of inter-integrated circuit (to be abbreviated as I²C hereinafter) communication protocol, and more particularly, to an optical communication interface module connected to a direct-current (DC) power terminal, an input/output (I/O) terminal and a ground terminal of an electric communication interface module of I²C communication protocol, to perform optical communication. Here, the I/O terminal refers to an I/O terminal to/from which a serial data signal or a serial clock signal of the I²C communication protocol is input/output.

2. Description of the Related Art

FIG. 1 shows waveforms for explaining an I²C communication protocol.

Referring to FIG. 1, the I²C communication protocol is a protocol for performing serial communication by only two channels for a serial data signal SDA and a serial clock signal SCL, without a channel for a control signal, unlike in a typical serial communication protocol. According to the I²C communication protocol, whenever the serial clock signal SCL becomes a logic state of ‘1’ (a higher voltage level V_(H)), the state of the serial data signal SDA is set.

A time t1 at which the serial data signal SDA falls from a logic value of ‘1’ to a logic value of ‘0’ (a lower voltage level V_(L)), while the serial clock signal SCL has a logic value of ‘1’, is a starting time of a data packet. A time t14 at which the serial data signal SDA rises from a logic value of ‘0’ to a logic value of ‘1’ while the serial clock signal SCL has a logic value of ‘1’, is a terminating time of a data packet. Thus, in the time period of t1–t14 for a data packet, the serial data signal SDA must not undergo logic transition while the corresponding serial clock signal SCL.

Data having a logic value of ‘1’, are sequentially transmitted or received for the duration of t2–t3 in which the serial clock signal SCL has a logic value of ‘1’, data having a logic value of ‘0’ for the duration of t4–t5, data having a logic value of ‘1’ for the duration of t10–t11, and data having a logic value of ‘1’ for the duration of t12–t13, respectively.

FIG. 2 shows general electric communication interface modules of I²C communication protocol, which are modules for a serial data signal SDA, and are the same as those for a serial clock signal SCL. In FIG. 2, reference mark SDA1 IN denotes a serial data input signal supplied from a first module El1, SDA1 OUT a serial data output signal supplied from the first module El1, SDA2 IN a serial data input signal supplied from a second module El2, and SDA2 OUT a serial data input signal supplied from the second module El2, respectively.

A procedure in which the serial data output signal SDA1 OUT in the first module El1 is transmitted from the first module El1 and received at the second module El2, will now be described with reference to FIG. 2.

If the first serial output data SDA1 OUT is at a logic ‘1’ level, a first transistor TR₁ is turned ON. Accordingly, a current flows from a second power terminal VCC 2 of the second module El2 to a ground terminal via a pull-up resistor Rp₂, a second terminal P2, an electric current line CL, the first transistor TR₁ and a first current source CS₁. Thus, the potential of a second terminal P2 is decreased, so that the second serial data input signal SDA2 IN received through an inverter B₂ of the second module El2 becomes at a logic ‘1’ level, that is, the current flows in a direction indicated by D1.

Conversely, if the first serial output data SDA1 OUT is at a logic ‘0’ level, the first transistor TR₁ is turned OFF. Accordingly, the potentials of the first and second terminals P1 and P2 are increased, so that the second serial data input signal SDA2 IN received through the inverter B₂ of the second module El2 becomes at logic ‘0’ level.

The above-described transmission/reception procedure is the same as a procedure in which the serial data output signal SDA2 OUT in the second module El2 is transmitted from the second module El2 and received at the first module El1. The transmission/reception procedure of the serial clock signal SCL is also the same as described above.

According to the conventional electric communication interface module, the communication speed is reduced due to the internal resistance of the current line CL itself and the maximum communication path becomes shorter.

SUMMARY OF THE INVENTION

To solve the above problems, it is an objective of the present invention to provide an optical communication interface module, connected to an electric communication module of an I²C communication protocol to perform optical communication, thereby increasing the communication speed and the maximum communication path.

To accomplish the above object of the present invention, there is provided an optical communication interface module connected to a direct-current (DC) power terminal, an input/output (I/O) terminal and a ground terminal, to perform optical communication. The module includes a PNP transistor for transmission, a pull-up device, a photo generator device, a photoelectric converter, and first and second NPN transistors for reception. The PNP transmission transistor has its base connected to the I/O terminal and its collector connected to the ground terminal. The pull-up device with its one end connected to the DC power terminal, scales down the voltage in proportionate to the amount of the current flowing therein. The photo generator device with its anode connected to the opposite end of the pull-up device and its cathode connected to the emitter of the transmission transistor, generates light to be transmitted, according to the current flowing therein. The photoelectric converter converts the light received from the photo generator devices of the counter-party's optical communication module into an electrical signal. The first transistor for reception with its collector connected to the anode of the photo generator device and its emitter connected to the ground terminal, has its base driven by output signals of the photoelectric converter. The second transistor for reception with its collector connected to the I/O terminal and its emitter connected to the ground terminal, has its base driven by an output signal of the photoelectric converter.

According to the present invention, since the optical communication interface module is connected to the electric communication interface module of an I²C communication protocol to thus perform optical communication, the communication speed can be enhanced and the communication path can be increased as maximum as possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:

FIG. 1 is a timing diagram for explaining an I²C communication protocol;

FIG. 2 is a circuit diagram of general electric communication interface modules of an I²C communication protocol; and

FIG. 3 is a circuit diagram illustrating the state in which optical communication modules according to the present invention are connected to the electric communication interface modules shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3 illustrates the state in which optical communication modules according to the present invention are connected to the electric communication interface modules shown in FIG. 2. In FIG. 3, the same reference marks as those in FIG. 2 denote the same functional elements. Optical communication interface modules Ol1 and Ol2 are for a serial data signal SDA, and are the same as those for a serial clock signal SCL.

Referring to FIG. 3, the optical communication interface modules Ol1 and Ol2 are modules, which are connected to DC power terminals VCC 1 and VCC 2, input/output (I/O) terminals P1 and P2 and ground terminals of the electric communication interface modules of I²C communication protocol, respectively, to perform optical communication. The respective modules Ol1 and Ol2 include PNP transistors TR₁₁ and TR₂₁ for transmission, pull-up devices Rp₁₁ and Rp₂₁, laser diodes LD₁ and LD₂ as photo generators, photo diodes PD₁ and PD₂ as photoelectric converters, first NPN transistors TR₁₂ and TR₂₂ for reception, and second NPN transistors TR₁₃ and TR₂₃ for reception.

The PNP transistors TR₁₁ and TR₂₁ for transmission with their bases connected to the I/O terminals P1 and P2 and their collectors connected to the ground terminals. The pull-up devices Rp₁₁ and Rp₂₁ having their one ends connected to the DC power terminals VCC 1 and VCC 2, scale down the voltages in proportionate to the amount of the current flowing therein. The laser diodes LD₁ and LD₂ with their anodes connected to the opposite ends of the pull-up devices Rp₁₁ and Rp₂₁ and their cathodes connected to emitters of the PNP transistors TR₁₁ and TR₂₁, generate light to be transmitted, according to the current flowing therein. The photo diodes PD₁ and PD₂ convert light received from the laser diodes LD₁ and LD₂ of the counter-party's optical communication module into electrical signals. The first NPN transistors TR₁₂ and TR₂₂ with their collectors connected to anodes of the laser diodes LD₁ and LD₂ and their emitters connected to the ground terminals, have their bases driven by output signals of the photo diodes PD₁ and PD₂. The second NPN transistors TR₁₃ and TR₂₃ with their collectors connected to the I/O terminals P1 and P2 and their emitters connected to the ground terminals, have their bases driven by output signals of the photo diodes PD₁ and PD₂.

The bases of the first NPN transistors TR₁₂ and TR₂₂ and the bases of the second NPN transistors TR₁₃ and TR₂₃ are commonly connected to each other to then be connected to one ends of resistors R₁₁ and R₂₁ for adjusting a current. The cathodes of the photo diodes PD₁ and PD₂ are connected to the DC power terminals VCC 1 and VCC 2, respectively, and the anodes thereof are connected the input terminals of first and second amplifiers 11 and 12, respectively. The first and second amplifiers 11 and 12 amplify the output signals of the photo diodes PD₁ and PD₂ with a predetermined amplification degree, and the amplified signals are applied to the bases of the first NPN transistors TR₁₂ and TR₂₂ and the second NPN transistors TR₁₃ and TR₂₃ via the resistors R₁₁ and R₂₁.

Now, a procedure in which the serial data output signal SDA1 OUT in the first electric communication module El1 is transmitted from the first optical communication module Ol1 and then received at the second optical communication module Ol2 via an optical cable to then be input to the second electric communication module El2, will be described with reference to FIG. 3.

If the first serial output data SDA1 OUT is at a logic ‘0’ level, a first transistor TR₁ is turned OFF. Accordingly, the first PNP transistor TR₁₁ is turned OFF so that a current does not flow in the first laser diode LD₁, and no light is thus generated. Thus, the second photo diode PD₂ of the second optical communication interface module Ol2 are turned OFF, so that the first and second NPN transistors TR₂₂ and TR₂₃ of the second optical communication interface module Ol2 are turned OFF. Also, as the second NPN transistor TR₂₃ is turned OFF, a high voltage is applied to the terminal P2. Thus, the second serial data input signal SDA2 IN received through the inverter B₂ of the second electric communication module El2 becomes at a logic ‘0’ level.

Conversely, if the first serial output data SDA1 OUT is at a logic ‘1’ level, the first PNP transistor TR₁ is turned ON. Accordingly, the first PNP transistor TR₁₁ is turned ON so that a current flows in the first laser diode LD₁, and light is thus generated. The light emitted from the first laser diode LD₁ is transmitted through the optical cable OC so that the second photo diode PD₂ of the second optical communication interface module Ol2 is turned OFF. Accordingly, the current flows from the second DC power terminal VCC 2 to the bases of the first and second NPN transistors TR₂₂ and TR₂₃ via the second photo diode PD₂, the second amplifier 21 and the resistor R₂₁. Also, since the first and second NPN transistors TR₂₂ and TR₂₃ are turned ON, the current flows from the second DC power terminal VCC 2 to the ground terminal via the pull-up resistor Rp₂ of the second electric communication interface module El2, the terminal P2 and the second NPN transistor TR₂₃, and to the ground terminal via the pull-up resistor Rp₂₁ of the second optical communication interface module Ol2 and the second NON transistor TR₂₂, respectively. Accordingly, as a low voltage is applied to the terminal P2, the second serial data input signal SDA2 IN received through the inverter B₂ of the second electric communication module El2 becomes at a logic ‘1’ level.

The above-described transmission/reception procedure is the same as a procedure in which the serial data output signal SDA2 OUT in the second module El2 is transmitted from the second optical communication interface module Ol2 and received at the first optical communication interface module Ol1. The transmission/reception procedure of the serial clock signal (SCL of FIG. 1) is also the same as described above.

The types of the transistors shown in FIG. 3, that is, NPN and PNP types, may be reversed according to the modification of enable logic and circuits.

According to the present invention, since the optical communication interface module is connected to the electric communication interface module of an I²C communication protocol to thus perform optical communication, the communication speed can be enhanced and the maximum communication path can be increased as much as possible. 

1. An optical communication interface module connected to a direct-current (DC) power terminal, an input/output (I/O) terminal and a ground terminal, to perform optical communication, the module comprising: a transistor for transmission having its base connected to the I/O terminal and its collector connected to the ground terminal; a pull-up device having its one end connected to the DC power terminal, for scaling down the voltage in proportionate to the amount of the current flowing therein; a photo generator device with its anode connected to the opposite end of the pull-up device and its cathode connected to the emitter of the transmission transistor, for generating light to be transmitted, according to the current flowing therein; a photoelectric converter for converting the light received from the photo generator devices of the counter-party's optical communication module into an electrical signal; a first transistor for reception with its collector connected to the anode of the photo generator device and its emitter connected to the ground terminal, the first transistor having its base driven by output signals of the photoelectric converter; and a second transistor for reception with its collector connected to the I/O terminal and its emitter connected to the ground terminal, the second transistor having its base driven by an output signal of the photoelectric converter.
 2. The optical communication interface module according to claim 1, wherein the bases of the first and second reception transistors are commonly connected to each other, and an amplifier for amplifying the output signal of the photoelectric converter with a predetermined amplification degree and applying the amplified signal to the bases of the first and second reception transistors, is provided between the common connection point of the bases of the first and second reception transistors and the photoelectric converter. 